The explosion on chemical storage tank at Packaging Corporation of America, Tomahawk, Wisconsin, on July 29, 2008, which killed three people, has shown how chemical storage tanks could put hazard into reality.
The above accident did not represent the entire potential hazards associated with the presence of chemical storage tanks in a chemical plant. In addition, the condition become worst when chemical stored in the tanks are flammable, combustible, corrosive or even toxic.
Because chemical storage tanks present in all chemical plants, improvement of their safety is very important. That's why this article is written.
Safety tips that I will tell you in this article are extracted from the US Chemical Safety Board bulletin issued in February 2010 entitled Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks, and also from other resources.
1. Chemical storage tanks are made of compatible material that will not react with stored chemical.
2. Be careful when you decide to select tank fabricator or manufacturer. Check their products quality and track record.
3. Always refer to appropriate standards when you are going to go into design phase.
4. Some of tank ruptures were caused by defective welds. Effective monitoring and checking including welding test during tanks fabrication are vital.
5. A safe distance between each tank is provided. It will prevent chain reaction when fire occurs at one tank.
6. There should be at least two level indicators installed on chemical tanks to avoid level instrument failure. It had better to provide level glass or something like that for worker to check manually.
7. Do not forget to ensure there are also temperature indicators installed on the tanks. Decomposition reaction, which releases heat, can be easily detected.
8. Instrument calibration is required to ensure correct reading. Set up regular schedule for it.
9. Venting facilities are installed to accommodate over pressure or vacuum.
10. Check regularly the venting facilities. Make sure that they are not blocked by dirt and work properly.
11. Ovoid overfilling tanks. It can be achieved by a combination of manual monitoring or indicating, high level alarm and automatic shut off system.
12. Thickness and welding check may be necessary in some cases, suppose when contained chemical is a highly corrosive. Refer to applicable standards and experts at the field.
13. When you plan to do hydrostatic pressure test or full water test, consider tanks condition and their lifetime. Pressure standard may be slightly lower than the first hydrostatic test.
14. If possible use alternative methods to avoid hot work in and around the tanks.
15. When hot work will be conducted in tank that contains flammable liquid or suspected to be contain flammable liquid, ensure that all possible entrances or inlets have already been isolated. It is applied not only for the tank itself but all connected piping and surrounding the tank. If necessary, drain out all the flammable liquid from the tank and related piping.
16. Monitor flammable gas and vapor before and during the hot work. Use combustible gas detector.
17. Use written permit before hot work can be started in the storage tank.
18. Ensure that all personnel involved in the hot work are trained well, including contractor workers.
19. Secondary containment such as dike is necessary. Dike will reduce the possibility of bigger safety and environment problems when a chemical storage tank is ruptured.
20. Do not operate any storage tank more than allowable maximum operating level as it is designed to. If you frequently perform such operation, then it is strongly recommended to install new storage tank to avoid tank rupture.
21. Any drain valve installed on tanks should be equipped with valve locks, blind flanges or caps to avoid accidental opening or valve failure.
22. Catastrophic chemical storage tank is a kind of emergency condition. So it requires you to establish an emergency response plan.
Inadequate design, fabrication, construction, inspection and maintenance can lead to chemical storage tanks failure. Apply these safety tips consistently. In addition, you can make them as safety inspection checklist for the entire chemical storage tanks inside your chemical plant.
Lukman Nulhakiem is a chemical engineer who has many experiences in hazard recognition and hazard control studies. Learn more about safety tips for workplaces, visit his blog chemicalplantsafety.net.
No matter how good the quality of your chemical storage tanks are, accidents can still occur if you do not follow safety rules and guidelines. That’s why it’s important that you always check your equipment and facilities. Consider following the safety tips mentioned above to make sure that your plant’s operations are safe.
ReplyDeleteRichelle Loughney